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22 """Block device abstraction - base class and utility functions"""
26 from ganeti import objects
27 from ganeti import constants
28 from ganeti import utils
29 from ganeti import errors
32 class BlockDev(object):
33 """Block device abstract class.
35 A block device can be in the following states:
36 - not existing on the system, and by `Create()` it goes into:
37 - existing but not setup/not active, and by `Assemble()` goes into:
38 - active read-write and by `Open()` it goes into
39 - online (=used, or ready for use)
41 A device can also be online but read-only, however we are not using
42 the readonly state (LV has it, if needed in the future) and we are
43 usually looking at this like at a stack, so it's easier to
44 conceptualise the transition from not-existing to online and back
47 The many different states of the device are due to the fact that we
48 need to cover many device types:
49 - logical volumes are created, lvchange -a y $lv, and used
50 - drbd devices are attached to a local disk/remote peer and made primary
52 A block device is identified by three items:
53 - the /dev path of the device (dynamic)
54 - a unique ID of the device (static)
55 - it's major/minor pair (dynamic)
57 Not all devices implement both the first two as distinct items. LVM
58 logical volumes have their unique ID (the pair volume group, logical
59 volume name) in a 1-to-1 relation to the dev path. For DRBD devices,
60 the /dev path is again dynamic and the unique id is the pair (host1,
63 You can get to a device in two ways:
64 - creating the (real) device, which returns you
65 an attached instance (lvcreate)
66 - attaching of a python instance to an existing (real) device
68 The second point, the attachment to a device, is different
69 depending on whether the device is assembled or not. At init() time,
70 we search for a device with the same unique_id as us. If found,
71 good. It also means that the device is already assembled. If not,
72 after assembly we'll have our correct major/minor.
75 def __init__(self, unique_id, children, size, params):
76 self._children = children
78 self.unique_id = unique_id
86 """Assemble the device from its components.
88 Implementations of this method by child classes must ensure that:
89 - after the device has been assembled, it knows its major/minor
90 numbers; this allows other devices (usually parents) to probe
91 correctly for their children
92 - calling this method on an existing, in-use device is safe
93 - if the device is already configured (and in an OK state),
94 this method is idempotent
100 """Find a device which matches our config and attach to it.
103 raise NotImplementedError
106 """Notifies that the device will no longer be used for I/O.
109 raise NotImplementedError
112 def Create(cls, unique_id, children, size, params, excl_stor):
113 """Create the device.
115 If the device cannot be created, it will return None
116 instead. Error messages go to the logging system.
118 Note that for some devices, the unique_id is used, and for other,
119 the children. The idea is that these two, taken together, are
120 enough for both creation and assembly (later).
122 @type unique_id: 2-element tuple or list
123 @param unique_id: unique identifier; the details depend on the actual device
125 @type children: list of L{BlockDev}
126 @param children: for hierarchical devices, the child devices
128 @param size: size in MiB
130 @param params: device-specific options/parameters
131 @type excl_stor: bool
132 @param excl_stor: whether exclusive_storage is active
134 @return: the created device, or C{None} in case of an error
137 raise NotImplementedError
140 """Remove this device.
142 This makes sense only for some of the device types: LV and file
143 storage. Also note that if the device can't attach, the removal
147 raise NotImplementedError
149 def Rename(self, new_id):
150 """Rename this device.
152 This may or may not make sense for a given device type.
155 raise NotImplementedError
157 def Open(self, force=False):
158 """Make the device ready for use.
160 This makes the device ready for I/O. For now, just the DRBD
163 The force parameter signifies that if the device has any kind of
164 --force thing, it should be used, we know what we are doing.
169 raise NotImplementedError
172 """Shut down the device, freeing its children.
174 This undoes the `Assemble()` work, except for the child
175 assembling; as such, the children on the device are still
176 assembled after this call.
179 raise NotImplementedError
181 def SetSyncParams(self, params):
182 """Adjust the synchronization parameters of the mirror.
184 In case this is not a mirroring device, this is no-op.
186 @param params: dictionary of LD level disk parameters related to the
189 @return: a list of error messages, emitted both by the current node and by
190 children. An empty list means no errors.
195 for child in self._children:
196 result.extend(child.SetSyncParams(params))
199 def PauseResumeSync(self, pause):
200 """Pause/Resume the sync of the mirror.
202 In case this is not a mirroring device, this is no-op.
205 @param pause: Whether to pause or resume
210 for child in self._children:
211 result = result and child.PauseResumeSync(pause)
214 def GetSyncStatus(self):
215 """Returns the sync status of the device.
217 If this device is a mirroring device, this function returns the
218 status of the mirror.
220 If sync_percent is None, it means the device is not syncing.
222 If estimated_time is None, it means we can't estimate
223 the time needed, otherwise it's the time left in seconds.
225 If is_degraded is True, it means the device is missing
226 redundancy. This is usually a sign that something went wrong in
227 the device setup, if sync_percent is None.
229 The ldisk parameter represents the degradation of the local
230 data. This is only valid for some devices, the rest will always
231 return False (not degraded).
233 @rtype: objects.BlockDevStatus
236 return objects.BlockDevStatus(dev_path=self.dev_path,
242 ldisk_status=constants.LDS_OKAY)
244 def CombinedSyncStatus(self):
245 """Calculate the mirror status recursively for our children.
247 The return value is the same as for `GetSyncStatus()` except the
248 minimum percent and maximum time are calculated across our
251 @rtype: objects.BlockDevStatus
254 status = self.GetSyncStatus()
256 min_percent = status.sync_percent
257 max_time = status.estimated_time
258 is_degraded = status.is_degraded
259 ldisk_status = status.ldisk_status
262 for child in self._children:
263 child_status = child.GetSyncStatus()
265 if min_percent is None:
266 min_percent = child_status.sync_percent
267 elif child_status.sync_percent is not None:
268 min_percent = min(min_percent, child_status.sync_percent)
271 max_time = child_status.estimated_time
272 elif child_status.estimated_time is not None:
273 max_time = max(max_time, child_status.estimated_time)
275 is_degraded = is_degraded or child_status.is_degraded
277 if ldisk_status is None:
278 ldisk_status = child_status.ldisk_status
279 elif child_status.ldisk_status is not None:
280 ldisk_status = max(ldisk_status, child_status.ldisk_status)
282 return objects.BlockDevStatus(dev_path=self.dev_path,
285 sync_percent=min_percent,
286 estimated_time=max_time,
287 is_degraded=is_degraded,
288 ldisk_status=ldisk_status)
290 def SetInfo(self, text):
291 """Update metadata with info text.
293 Only supported for some device types.
296 for child in self._children:
299 def Grow(self, amount, dryrun, backingstore):
300 """Grow the block device.
302 @type amount: integer
303 @param amount: the amount (in mebibytes) to grow with
304 @type dryrun: boolean
305 @param dryrun: whether to execute the operation in simulation mode
306 only, without actually increasing the size
307 @param backingstore: whether to execute the operation on backing storage
308 only, or on "logical" storage only; e.g. DRBD is logical storage,
309 whereas LVM, file, RBD are backing storage
312 raise NotImplementedError
314 def GetActualSize(self):
315 """Return the actual disk size.
317 @note: the device needs to be active when this is called
320 assert self.attached, "BlockDevice not attached in GetActualSize()"
321 result = utils.RunCmd(["blockdev", "--getsize64", self.dev_path])
323 ThrowError("blockdev failed (%s): %s",
324 result.fail_reason, result.output)
326 sz = int(result.output.strip())
327 except (ValueError, TypeError), err:
328 ThrowError("Failed to parse blockdev output: %s", str(err))
332 return ("<%s: unique_id: %s, children: %s, %s:%s, %s>" %
333 (self.__class__, self.unique_id, self._children,
334 self.major, self.minor, self.dev_path))
337 def ThrowError(msg, *args):
338 """Log an error to the node daemon and the raise an exception.
341 @param msg: the text of the exception
342 @raise errors.BlockDeviceError
348 raise errors.BlockDeviceError(msg)
351 def IgnoreError(fn, *args, **kwargs):
352 """Executes the given function, ignoring BlockDeviceErrors.
354 This is used in order to simplify the execution of cleanup or
358 @return: True when fn didn't raise an exception, False otherwise
364 except errors.BlockDeviceError, err:
365 logging.warning("Caught BlockDeviceError but ignoring: %s", str(err))